Processes of manufacturing ammonium phosphate fertilizer using a variety of techniques are well known in the art and have been described in the following U.S. patents:
______________________________________ 2,755,176 2,904,342 2,950,961 3,044,851 3,171,733 3,228,752 3,264,085 3,366,127 3,375,063 3,382,059 3,420,624 3,464,808 3,562,778 3,677,734 3,733,191 3,922,157 4,104,362 ______________________________________
The disclosures of the above patents are incorporated by reference herein.
In processes of making ammonium phosphate fertilizer, it is desirable to conduct the reaction under conditions which form a significant amount of ammonium polyphosphate in the reaction product. The polyphosphates are desirable, particularly where merchant grade wet process phosphoric acid is used, due to the sequestering effect that the polyphosphates have on the metal ion impurities which are present in the wet process acid. If the impurities are not sequestered, gelatinous precipitates can form over time in the liquid ammonium phosphate fertilizer, creating difficulties in its use. The gelatinous precipitates can clog pipes in storage and transportation equipment and in the fertilizer applying machinery, which increases the cost of using the liquid fertilizer. In some cases, particularly where the concentration of impurities is high, solidification of the fertilizer may occur.
Applicant has discovered a process of manufacturing ammonium phosphate fertilizer in a single stage reaction vessel which at least partially utilizes the heat of ammoniation to dehydrate the phosphoric acid sufficiently that adequate quantities of polyphosphate are formed in the reaction product. The polyphosphate formed produces a stable liquid ammonium phosphate fertilizer which may be transported and stored at ambient temperatures for substantial lengths of time without significant precipitation or solidification of the product. The liquid fertilizer can be shipped under ambient conditions to remote sites where it can be mixed to form specific blends of fertilizer. The product has high nutrient properties as a fertilizer and the high concentration of nutrients is beneficial from a cost of transportation standpoint.